Smarty pants, I really could use your help! 350 Mag trouble SOLVED?? MAJOR UPDATE

Wildboating

Thanks Al!

bigmike

GUYS, I HAVE THE IDENTICAL PROBLEM ON MY 342 EXCEPT MINE IS OPPOSITE YOURS, THE DIFFERANCE IS I DO GET UP ON PLANE, IF MY TANKS ARE FULL, THE BOAT REALLY STRUGGLES BUT ONCE I AM UP, THE PORT ENGINE SLOWLY REACHES THE STARBOARD ENGINE WRIGHT UP TO 4800 RPM AND 38MPH, IT JUST SEEMS LIKE IT DOES NOT WANT TO HELP THE OTHER ENGINE, I HAD IT CHECKED BY THE DEALER AND HE SAYS EVERYTHING IS FINE BUT I KNOW THERE IS SOMETHING, SHE IS ON BLOCKS NOW FOR THE WINTER BUT I WILL SURELY LOOK AT EVERYTHING YOU LADS HAVE BEEN TALKING ABOUT

Black_Diamond

What prop pitch are you running?

Wildboating

Unfortunately I feel like my 4th and final service shop is also going to be a flop.   Who is the best of the best in Ohio?   I really want this low rpm issue resolved.  No one seems to be able to figure out why and now after telling the 4th mechanic exactly a list of what all has been done he decided to replace the dist, cap again knowing this has already been done twice.  Tired of throwing money away.    I wish Al was available to hire for an out of town job.    Can anyone suggest someone, someplace that has the best of the best.  THis can not be unsolveable / unfixable.

Wildboating

@Black_Diamond
The props were replaced 1st to fix the issue.  They are 22p 4x4s now from hill.   This is only on 1 motor.   I know this thread is long, that's how many attempts have been made with no luck.

Wildboating

@Alswagg. The shop is telling me you can't set a base timing on these motors.  There is no place to set it / check it.   Is this true?

Wildboating

We are getting 24* advance timing on the ecu.   The problematic motor still hesitates and pops in nuetral with throttle blips.   The good motor revs freely.

reneechris14

I did my injectors last week because port motor could not keep up down about 500rom.now I'm 200 rpms down on the starboard motor but that's ok 4900 To 5100 is to fast any way.base timing is set buy moving the distributor. 10° at 650rpm.so yes it can be set.paid 300 bucks on ebay all 8 injectors. Compression test all cylinders 180psi.

Liberty44140

Hi @Wildboating Cleveland has been a tough spot for good mechanics. I'm sure you already have used the merc dealer, ivancic? Past that the better mechanics are going to be in Marblehead/Sandusky. I've always heard good things about Dubberts who is a Mercruiser dealer. I think here may be one in Lorain? Sorry to hear about your troubles, I was wondering if and how this was resolved. 

Wildboating

@reneechris14. All new injectors already.   

Wildboating

@Liberty44140.  Ivanic looked at it then decided the dist was bad and told me it was fixed.   I picked up the boat and went for a ride, I found the exact same conditions.  I reported back and then they never showed up again.   

Wildboating

Does anyone have a how to video or PDF on setting the timing.   I can't believe I'm being told there is no way to set / check base timing if you can.  So frustrating..   I will look up dubberts.

Wildboating

Found this online, does this look right?

V6 and V8 EFI Models (EFI Ignition)

Two items of test equipment are required: an inductive pickup timing light and one of either a Scan Tool, Marine Diagnostic Code Tool or MerCruiser Special Timing Tool (Quicksilver 91-805747A1).
1. Connect timing light (91-99379 or similar) to No. 1 spark plug wire. Connect power supply leads, if applicable, on light to 12 volt battery. Refer to Specifications – “Engine Rotation and Firing Order,” for cylinder numbering and location.
2. Connect a shop tachometer to engine.

NOTE: Before starting engine make sure the timing tab and mark, or marks, on crankshaft damper are clean. Chalk or white paint on timing marks may help visibility.

NOTE: If NOT Using MerCruiser Timing Tool: With engine running, set the scan tool or Marine Diagnostic Code Tool to the SERVICE MODE and follow manufacturer’s instructions. On 350 Mag MPI Model, engine RPM will automatically increase to a higher RPM. You do not have to increase it manually, as stated in the following steps.

3. Connect the Timing Tool (or appropriate tool, as listed above) to the DLC connector (in the electrical box or on the electrical bracket) of the wiring harness.
4. Start the engine. Allow it to reach normal operating temperature.
5. On all models except 350 Mag MPI: Manually adjust the engine throttle to 1800 RPM.
6. Aim timing light at timing tab, located on the timing gear cover and crankshaft torsional damper. Check the timing. Refer to “Specifications.”
7. Loosen the distributor clamp bolt enough to just be able to rotate the distributor with some resistance.
8. Aim timing light at timing tab and recheck location of timing mark. Slowly rotate the distributor clockwise or counterclockwise to adjust the timing to specified degrees.
9. Aim timing light at timing tab and recheck location of timing mark. Repeat Step 8 until timing is correct. Torque distributor hold down bolt to 30 lb. ft. (40 N.m).
10. Manually close the throttle to bring engine RPM back to idle.

IMPORTANT: Be sure to disconnect MerCruiser Special Timing Tool from the DLC connector, or set the tool to NORMAL MODE if using the Scan Tool or Marine Diagnostic Code Tool, before attempting to resume normal operations. If the MerCruiser Special Timing Tool is left in pace or the setting of the tool remains in SERVICE MODE, the ignition system will operate only in the “Service Mode”. This means that the additional timing advance features would not function.

11. Disconnect the MerCruiser Special Timing Tool from the DLC connector. If using the Scan Tool or Marine Diagnostic Code Tool, set the tool to NORMAL MODE. Disconnect the tool.
12. Stop the engine. Turn ignition key to OFF position.
13. Remove timing light.

 

MERCRUISER PART DIAGRAMS

Wildboating

Where do i locate the timing light marks?  

randy56

I'm not trying to be smart, but the timing marks are at the same place as any other eng.  sometimes depending were the motor stops, you can see them if they are upon top. I'll take pic working on boat tonight. 

randy56

it's on the harmonic balancer in the front on eng. down low. attached pic of one.
 

http://www.jegs.com/i/JEGS/555/51652/10002/-1?CAWELAID=1710630867&CAGPSPN=pla&CAAGID=39714413703&CATCI=pla-293995373017&CATARGETID=230006180039220954&cadevice=c&gclid=CjwKCAjwsqjKBRBtEiwAkWyN3wvzpEJpDxjSfy4DCDjTIpH1AbAilUdlwiZmaa3EXNfWLLtbuFLphhoCWSoQAvD_BwE

reneechris14

went back and read from the beginning of the tread and you do the injectors the timing shows 24* witch is correct.and you have the scan tool it will show the timing if you scroll through.

Wildboating

The timing on both motors show 24* advance at wot.  

Wildboating

I will look tomorrow for the timing marks.  I have read so many other forums where others have also said these motors have non adjustable timing.   This may not be the problem, but i hope to find something there that says it is!

212rowboat

dont worry about timing marks... get a quality vacuum gauge...  you'll learn a lot about the engine using one... google for directions and various tests.

Wildboating

Drew,  if you go back to page 2 we did the vacuum test and i posted results.   You gave great instructions.   This is then Damnest thing..   I really just read the entire 7 pages over, I wanted to cry thinking of all the frusterations and money spent.  WHY CANT THIS BE FIXED>. UGH

212rowboat

some harmonic balancers, pretty much most of them made after EFI don't have marks.  you can change that by finding TDC#1 and marking it, then slapping a toothed measure on it (can pick up at a parts store; any for a sbc will work)... 

did you ever pull the timing cover and count teeth to make certain your camshaft/crank relationship is proper?  how about the timing chain? any slop?  sometimes chains have nylon inserts around the bearings in the links to make them quieter, and those things break or wear allowing full degrees of bad timing... also, some folks advance the shaft absurdly thinking they're making it perform- which may be the case with certain cams/lifter ratio's, but certainly not all and i doubt on a marine/sausage cam it's gonna help.  THIS crank/cam timing is much more likely an issue than ignition timing.  

davidbrooks

I just have to say you guys are AWESOME.  The experience and advice here is amazing.  

frenchship

Wildboating
I don't know how much money or hours you spend trying to fix that problem,but it has been a while trying to resolve it. Why don't you ship your boat to Al from what I know you guys lives about 4 hours away. If I am not mistaken.......
If I was in your situation that what I would have done.
Paul

212rowboat

Wildboating said:

@Alswagg. The shop is telling me you can't set a base timing on these motors.  There is no place to set it / check it.   Is this true?

that shop would be wrong. 

there should be a jumper in the harness that needs to be connected to set base timing... this removes the PCM or ignition modules advance... Al (as usual) is dead on that the scripted advance is 24*... add the base timing which should be 10~12* on some motors, or as low as 8* on others (I'm NOT getting that from a manual or publication, but from the air cleaner) which would make total advance in the low thirties- where it should be on a healthy engine... well tuned/built can be as high as 38*, but anything more than that is dangerous.  

here is something i'd like you to do.... simple and super easy to look over:  throttle body gaskets.... vacuum hose connections... PCV valves... those little nipples that terminate ports at the port... any slugs/threaded blanks in the intake manifold- pull them and tape them with fresh tape. 

i'm tellin' ya, get TWO quality vacuum gauges.. may run you $15ea.. connect both engines to one while under load and hold them side by side while underway at various speeds/revs... make a video and speak the RPMS and whether you're off step (plane) or on top... the video will allow you to compare them carefully and your voice over will help recall activity (whether turning- one under less load while doing so, ect..).  there isn't a lot that can't be determined by use of a vacuum gauge. it may not pinpoint, but it will certainly eliminate.  

also... have you ever checked the linkage at the TB to see if there is an obstruction or kink?  

Wildboating

I was setup with a new mechanic today, this guy seems very knowledgeable (technically knowledgeable).   He seems interested and willing to help albeit a hectic schedule already.    Otherwise If this guy can not resolve it I guess the trailer I just bought will be getting some use.

Wildboating

Looking at these two clips, does anyone see anything wrong?   I just noticed at wot or in this case 97% throttle my starboard is running 2gph less fuel.   Im no mechanic but is seems substantial.  

Wildboating

Is that due to the 400 less rpms or is the 400 less rpms due to 2gph less fuel.

Wildboating

212rowboat

if you're WOT, the engine has opened loop and is dumping fuel as hard as it can, as well as sparking at a pre-determined 'scripted' rate.  WOT doesn't sample environmental sensors- hence, open loop- strategies on the computer. blades wide open on the TB and fuel being pushed as hard as it can.

dude- your IAC- idle air control... check the variance on that...... swap them between engines and see what happens... clean the TB's with particular attention to the IAC port... make certain there is no unmetered air coming in... the position is mapped- the plunger has to be in the right position- which is why you'll hear them exercise when they're new- they fully seat and the PCM takes note- they'll open wide and the pcm takes note- the IAC is mapped... usually, you're good afterward... not always.. especially if you've cleaned them and disrupted that map...

question: why would one IAC not be at full duty when @ WOT? answer: it's getting air from somewhere else- un-metered.... you've got a vacuum leak somewhere, sir.  

check out your MAP- the LACK of variance there speaks to unmetered air.. 

also, your TPS voltage- dead same.... again, speaks to un-metered air... 

if it's NONE of these, you're gonna get dirty... oily, actually.  adjust your valve lash.  not with a tq wrench, but like a proper 'rodder.... warm her up... take valve covers off one at a time, get a towel and lay it over the valves you aren't working on... start engine... tighten down until the rockers are virtually silent, and then back off until you can detect the tiniest tick- then turn 1/8th turn tighter... all 8 pairs... if you check for all unmetered air leaks and find none, it's time to suspect valve seats.